Here's a thread to collect all the theme recommendations that are floating around the forums.
If you have a suggestion for an existing WordPress theme that you'd like to see available on WordPress.com, please post a link and brief description here.
To keep it manageable, here are a few ground rules for this thread:
1. No discussion, just pointers to specific themes please. You can discuss the themes elsewhere.
2. Please include a link to the theme home page or download page. No requests for hypothetical or unreleased themes, or changes to existing themes.
3. One theme per reply.
4. We can only consider themes that are clearly licensed under the GPL.
If you're not sure where to find GPL'd WordPress themes, themes.wordpress.net is a great start.
Please note that we can't accept all themes for various technical and quality reasons, but we will look at all the suggestions posted here.